Conservatory Heat Harvester

Conservatory Heat Harvester systems
The solar heat harvester system will very efficiently transfer hot solar heated air from high in your conservatory to your home at a typical annual running cost of £1, yes this is correct!

Before you order a Solar Heat Harvester System there are things you should consider:

If you wish to reduce home heating costs the first and most cost effective thing you can do is ensure that your attic floor has at least 300mm of insulation.

For Conservatory Heat Harvesting to work most efficiently there should be an airflow path route from the system fan mounted 'high' in the wall adjoining your ground floor conservatory where the air is hot, through to your home and, if possible, back into the conservatory at a low level.

If possible a second low air hole back into your conservatory enabling the cooler air to get back to the conservatory to be re-heated and re-circulated. Ideally this air return hole will be from a different, and if possible the coldest room in your home. If the room receiving the hot air is accessed by doors leaving the doors open will enable more of your home to be heated.

If it is not possible to have a return air valve to the conservatory and you home is relatively air tight you must ensure that the hot air can flow through your home, preferably at a low level, then exit to the outside somewhere from a cool room, this may be the location where the second air valve is fitted.

These diagrams show a typical Conservatory Heat Harvester installation and the wiring diagram.

Mullion Conservatory Heat Harvester system diagram

conservatory heat harvester system wiring diagram

We usually do not supply all the items your need to install your system as you can easily obtain them yourself at a lower cost and obtain items that suit your home's decor, these items are:

a)   the system fused ON OFF switch and mounting box

b)   a short length of twin and earth 1mm2 cable from the main supply to the fused On Off switch

c)   a short length of twin and earth 1mm² cable from the ON OFF switch to the Attic Heat Harvester Controller

d)   short length(s)- of plastic pipe of a diameter to suit the fan/blower that will be in the air holes that go through the wall preventing air escaping into the wall

e)   one or two gravity closing air vents

f)   sundry raw plugs and screws and parts

Installation Instructions – please read and understand these before you start work.

1   On both sides of the wall between the conservatory and your home carefully locate the desired position of the high conservatory hot air exit hole and if you can the low conservatory cool air return hole. The air return hole should preferably be quite a distance from the first hole. Take care to consider the position of window and door lintels as the holes must not be there.

2   Decide on your preferred location for the Attic Heat Harvester controller. This is generally fitted to a wall in the room adjoining your conservatory near to fan/blower about 1.5m from the floor making the controller key switches easy to operate and its display easy to see. We recommend that the room temperature sensor is be fitted in the same room as the return air vent to the conservatory.

Another thing to consider is the location of a suitable electrical supply power as it is easier to connect the controller to a nearby 230vac supply. The controller will be connected to the fan and to the conservatory and room temperature sensors cables, these will enter the controller from the rear right hand side and connect to the internal controller connectors J5 to J9 on the right side of the printed circuit board.

Conservatory Heat Harvester PCB circuit board

3   When you have determined the locations for the above items your can determine the minimum length of the cables you will require, you will need these dimensions to choose the cable lengths to order.

4   When you are confident that your desired hole positions are good drill small diameter centre hole(s) through the adjoining wall(s) to confirm that both hole positions are OK.

5   If you will be using a core drill to make the air flow holes skip steps 6 to 13.

6   If you are not going to use a core drill then skip steps 7 to 14 below, else make a thick wooden drilling jig to ensure that the holes you drill are perpendicular to the wall so the hole on the other side of the wall will be close to circular.

7   Get piece of wood that is larger than the hole you require and which is at least 25mm thick or preferably even thicker, you will use this to make a drilling jig.

8   Chose a drill suitable for the wall that is long enough to go through the wall and the drilling jig.

9   Draw a circle on the wood that is of a slightly smaller diameter than the fan/blower you will be using. Mark a number of holes around the circumference of the jig air hole that are just a little farther apart than the diameter of the long masonry drill you intend to use.

10   Using a wood drill, of the same diameter as the long masonry bit, drill holes around the circle that are perpendicular to the top of your drilling jig and close together but not overlapping.

11   Smooth the edges of the air hole using a stone chisel and hammer.

12   Temporarily screw the jig to the wall in the correct position.

13   Using the drilling jig drill perpendicular holes through the wall with the long masonry drill.

14   Repeat the last 2 steps for the air return hole

15   You should obtain and fit a short length(s) of PVC pipe, of at least the same diameter or larger diameter as your fan unit, to go through the wall(s) preventing hot air escaping into the wall. Alternatively you could use thin aluminium sheet to make the pipe.

16   If you wish to hide the controller system cables in the wall make channels in the wall for them.

17   We recommend that the Attic Heat Harvester 230vac power be fed via a separate fused (2 amp) isolating switch which is generally located just beneath the controller.

18   Make a backing board for the fan/blower unit and fit the fan to it.

19   Make mounting holes in the wall for raw plugs to mount the controller, the fused power switch, the fan mounting board, and the gravity air valves.

20   The Attic Heat Harvester Controller user connections are on the right hand side inside the enclosure – see the picture above.

21   After passing the fan cable through the hole to the controller location fit the fan and backing board to the conservatory wall. The fan/blower motor cable should be rated for at least 2 amps.

22   Connect the controller cables as shown in the wiring diagram above.

23   The solar heat harvester conservatory temperature sensor should be located in front of the fan in the conservatory to monitor the air temperature ensuring that it cannot be sucked into the fan. Run the connector end of the cable to the rear of the Attic Heat Harvester Controller location.

24   The solar heat harvester room temperature sensor should be located in the same area as the return air hole and approximately 1m from the floor. If there is no return air hole run this sensor cable to a cooler area of your home where the cooler air can exit.

25   Run the room temperature cable from the sensor location to the back of the controller.

26   Fit the gravity air vent(s) on the wall air exit sides of the air holes.

27   Carefully remove the front of the Attic Heat Harvester controller by loosening the four black corner screws.

28   Disconnect the 4 way connector to the front panel mounted keypad, and put the front panel aside.

29   Fit the controller and fused power switch to the wall after carefully checking that all system connections comply with the wiring diagram.

System commissioning

1   Initial commissioning acn be done without the front panel keyboard being fitted.

2   Temporarily disconnect the controller 4 way connector J8 for the initial test. Only the attic sensor J5, room sensor J6, and main power J9, connectors should be connected. See pcb photograph here.

3   Turn ON the power to the Attic Heat Harvester controller.

4   If the controller is connected correctly the green Power On LED should turn on, the display back light will turn on for 1 minute and the yellow LED (top left) should blink every second. The LCD display will sequentially display the 'Sign On' messages.

The 'firmware version number', then perform a self-test displaying any problems seen. If there are no problems the Current Time will be displayed as 0:00 giving you the option for 20 seconds of setting the time using the + and – keys, - this process can be aborted by pressing the front panel Mode key, then the current conservatory and room temperatures will be displayed.

5   If problems are detected with the 230vac supply voltage or with the temperature sensors they will be displayed and you should consult the Attic Heat Harvester Controller Manual' section 4 Systems Tests at for help. To select the controller 'built in test features' the front panel keypad will need to be connected. Problems need to be rectified before you can proceed to the next step.

6   If there are no problems the Current Time will be displayed as 0:00 and give you the option of setting the time using the + and – keys. This process can be aborted by pressing the front panel Mode key, then the attic and room temperatures will be displayed.:.

7   Turn OFF power to the system.

8   Connect the 4 way connector J8. If a 6 way connector had been fitted to J8 connect the 4 way connector to the bottom 4 pins 3 to 6.

9   Turn ON power to the system.

10   When room and conservatory temperatures permit the fan/blower will turn on after a short delay.

The Attic Heat harvester Controller has many user set parameters that enable you to configure the system to suit your installation and your needs. See section 3 Parameter setting mode at

The Attic Heat harvester Controller continually monitors your systems performance, see section 2 System Performance Display mode at

Enjoy your Solar Heat Harvesting System and the heating cost savings you will have in all your future years.

Thank you for helping future generations of mankind by reducing your carbon foot print.

To get the best from you system may we suggest you read and become familiar with the Attic Heat Harvester Controller Manual at